1. Field of the Invention
The present invention is directed to downloading data to mobile terminals. More specifically, the invention concerns pre-checking the availability of resources consumable in downloading data to mobile terminals.
2. Description of the Related Art
Mobile terminals, such as phones, PDA's and laptop computers, are increasingly being used to wirelessly download computer files, as from the Internet. These terminals often run on battery power, and the download of larger files can require more power than is available. Having a download terminate for lack of power can be annoying to the user, who has not only failed to complete the download but, in addition, has now expended all of the remaining energy in the device. Moreover, a resource other than power, such as time, may be at a premium. For example, the user may be limited in the amount of remaining airtime for the device, e.g. time allotted for this month, and may choose to avoid a download rather than initiate a download that exceeds the available remaining airtime.
Japanese Patent Application No. 11-119804 discloses a mobile terminal that maintains a memory table indexing minimum power levels against program identifiers. If the program being downloaded requires a minimum power level that exceeds the current remaining power level for the terminal, the download is stopped. However, power levels are checked only for a predetermined set of programs. If the user decides to download a program not included within the set, e.g., a program just learned of while on the Internet, the system does not perform its checking function. Another drawback is that the power levels used as a reference are fixed in the memory table. It is thus assumed that the size of a downloadable file remains constant, which is not the case. In addition, there is no adjustment for transient variances in the amount of energy needed for a download based on received signal strength and quality, transmission rate, bit error rate, distance from the receiver, etc.